What is CVE-2021-22555?

CVE-2021-22555 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10, classified as a Out-of-bounds Write flaw (CWE-787). CVE-2021-22555 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild.

What is the CVSS score for CVE-2021-22555?

CVE-2021-22555 has a CVSS score of 7.8 out of 10, rated High severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Is there a patch available for CVE-2021-22555?

Monitor the NIST NVD and your Linux distribution's security advisories for CVE-2021-22555 patch availability.

Is CVE-2021-22555 actively exploited?

Yes. CVE-2021-22555 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild with a CVSS score of 7.8 (High severity).

What is Out-of-bounds Write (CWE-787)?

The product writes data past the end or before the beginning of the intended buffer. See MITRE CWE for full details: https://cwe.mitre.org/data/definitions/787.html

CVE-2021-22555

High KEV — Actively Exploited

A heap out-of-bounds write affecting Linux since v2.6.19-rc1 was discovered in net/netfilter/x_tables.c. This allows an attacker to gain privileges or cause a DoS (via heap memory corruption) through user name space

Package Linux Kernel

Published 2021-07-07

Last modified 2026-06-17

CVSS version 3.1

Patch available

Awaiting data

CVSS 3.1 score

7.8

out of 10

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Vector string

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-787

CVE-2021-22555 is a Out-of-bounds Write vulnerability

What is Out-of-bounds Write?

The product writes data past the end or before the beginning of the intended buffer. Learn more on MITRE CWE

References

10 total

Packet Storm
http://packetstormsecurity.com/files/163878/Kernel-Live-Patch-Security-Notice-LSN-0080-1.html

Exploit Third Party Advisory VDB Entry
Packet Storm
http://packetstormsecurity.com/files/164155/Kernel-Live-Patch-Security-Notice-LSN-0081-1.html

Exploit Third Party Advisory VDB Entry
Packet Storm
http://packetstormsecurity.com/files/164437/Netfilter-x_tables-Heap-Out-Of-Bounds-Write-Privilege-Escalation.html

Exploit Third Party Advisory VDB Entry
Packet Storm
http://packetstormsecurity.com/files/165477/Kernel-Live-Patch-Security-Notice-LSN-0083-1.html

Exploit Third Party Advisory VDB Entry
GitHub
https://github.com/google/security-research/security/advisories/GHSA-xxx5-8mvq-3528

Exploit Third Party Advisory

Showing 5 of 10 references View all on NVD

Details

CVE ID CVE-2021-22555

Severity High

CVSS score 7.8 / 10

CVSS version 3.1

Published 2021-07-07

Modified 2026-06-17

KEV Yes

Patch Awaiting data

Package linux

Frequently asked questions

What is CVE-2021-22555?

CVE-2021-22555 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Out-of-bounds Write flaw (CWE-787) . CVE-2021-22555 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild.
What is the CVSS score for CVE-2021-22555?

CVE-2021-22555 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Is there a patch available for CVE-2021-22555?

Monitor the NIST NVD and your Linux distribution's security advisories for CVE-2021-22555 patch availability.
Is CVE-2021-22555 actively exploited?

Yes. CVE-2021-22555 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. It carries a CVSS score of 7.8 (High severity).